Well drilling apparatus



Aug. 16, 1938. D. DRISCCSLL WELL DRILLING APPARATUS Filed March 4, 19364 Sheets-Sheet l H16 Hilary Aug. 16, 1938. D DRISCOLL 2,127,108

WELL DRILLING APPARATUS Filed March 4, 1936 4 Shets-Sheet 2 a .Z'n enfor flaw/15 L. D2166 OLL Aug. 16, 1938. D. L. DRISCOLL v WELL DRILLINGAPPARATUS Filed March 4, 1936 4 Sheets-Sheet 3 1938- D. L. DRISCOLL2,127,108

WELL DRILLING APPARATUS Filed March 4, 1936 4 Sheets-Sheet 4 PatentedAug. 16, 1938 UNITED STATES WELL DRILLING APPARATUS Dennis L. Driscoll,Los Angeles, Calif., assignor to Lawrence F. Baash, Los Angeles, Calif.

Application March 4,

18 Claims.

This invention relates to well drilling apparatus and relates moreparticularly to a rotary table bushing and slips therefor. A generalobject of this invention is to provide an improved rotary table bushingand slip assembly that is particularly effective and long wearing.

Another object of this invention is to provide a practical rotary tablebushing and slip assembly in which the slips all have extensive andequal seating engagement with the bushing and have uniform grippingcontact with the pipe or object handled. The extensive engagement of theslips in the bushing allows the slips to be of light construction and ofsubstantial length.

Another object of the invention is to provide a master bushing for arotary table that has inclined grooves or slots in its interior ofuniform width throughout their lengths and slips shaped and proportionedto fit the slots whereby they may have extensive continuous engagementwith the walls of the slots while gripping the pipe and when in anyvertical position they may assume while contacting the pipe. Heretoforeit has been the usual practice to provide a round tapered opening or a,round opening of downwardly diminishing diameter in the bushing of arotary table to receive the pipe gripping slips. When a bushing isprovided with such a tapered opening there is only one vertical positionin which the slips have full cooperation with the walls of the bushingand when the slips assume different vertical positions as they often dowhen gripping a pipe, certain of the slips have only line contact orpartial contact with the bushing. In the assembly of my invention theslips have full surface contact with the walls of the bushing slotsregardless of the vertical positions they may assume when contacting thepipe.

Another object of this invention is to provide a slip receiving bushingfor a rotary table having an opening of uniform dimensions throughoutits length to more readily pass drill pipe protectors and other drillingequipment.

Another object of this invention is to provide an improved assembly of arotary table bushing and pipe gripping slips in which the slips cannotfoul one another and cannot turn or tilt laterally in the bushing.

Another object of this invention is to provide a rotary table bushingand slip assembly in which all of the several slips have uniformgripping engagement with the object or pipe throughout their lengths todependably grip the pipe without tending to distort it.

Another object of this invention to provide 1936, Serial No. 67,080

a rotary table bushing and slip assembly that embodies practicaleffective rests or cradles for the slips when they are removed from thebushing which cradles support the slip in positions for immediateinsertion in the slots of the bushing.

Another object of this invention is to provide slips having simple andvery inexpensive replaceable pipe engaging parts or liners whereby theymay be readily reconditioned or adapted for the handling of pipe ofvarious diameters.

The various other objects and features of my invention will be fullyunderstood from the following detailed description of typical preferredforms and applications of my invention, throughout which descriptionreference is made to the accompanying drawings, in which:

Fig. 1 is a top or plan elevation of one form of assembly provided bythis invention. Fig. 2 is an enlarged fragmentary horizontal detailedsectional view taken substantially as indicated by line 22 on Fig. 3.Fig. 3 is an enlarged fragmentary vertical detailed sectional view takenas indicated by line 3-3 on Fig. 1. Fig. 4 is a fragmentary elevationview of the upper portion of one of the cradles being a view takensubstantially as indicated by line 44 on Fig. 3. Fig. 5 is an enlargedfragmentary horizontal detailed sectional View taken as indicated byline 55 on Fig. 3. Fig. 6 is a topor plan elevation of another form ofassembly provided by this invention. Fig. 7 is a fragmentary verticaldetailed sectional view taken as indicated by line I'I on Fig. 6. Fig. 8is a fragmentary horizontal detailed sectional view taken as indicatedby line 8-8 on Fig. 7. Fig. 9 is a perspective view of the inner side ofone of the bushing sections of the form of the invention illustrated inFigs. 6, 7 and 8; and Fig. 10 is a top or plan elevation of stillanother form of assembly provided by the invention.

The form of the invention illustrated in Figs. 1 to 5, inclusive, of thedrawings, includes generally, a bushing I0 for arrangement in a rotarytable T and having slots II in its interior, slips I2 adapted to fit inthe slots II to grip a pipe P or the like, and rests or cradles I3 forcarrying the slips l2 when they are removed from the bushing Ill.

The bushing 10 is what is usually termed a master bushing and isintended for arrangement in the opening M of the rotary table T. In'theparticular form of the invention being described the bushing I0 is roundor cylindrical tofit the correspondingly shaped opening M of the tableT. An annular outwardly projecting flange I5 is provided at the upperend'of the bushing H) to fit in an enlargement or annular groove IS inthe upper end of the table opening I4 and to seat on a shoulder |6 inthe opening I4. Lugs l7 project radially from the periphery of theflange It: to fit bayonet slots I8. in the table T. Lock blocks l9 areinserted in the bayonet slots |8 to lock the lateral arms of the lugs IIin the lateral portions of the slots I8. A rotary table of the generaltype just described having bayonet slots for receiving lugs on a bushingis fully described and claimed in'my co-pending application entitledRotary well drilling apparatus, filed November 11, 1935, Serial No.49,175.

t is to be understood that the bushing ||l being described may be shapedto fit any type of rotary table opening without departing from theinvention. It is to be noted that when the bushing I is designed for usein the particular rotary table T illustrated that it has a cylindricalperiphery throughout its length and, therefore, has a substantial anduniform wallthickness. The Wall of the bushing I0 may be chambered andprovided with suitable internal reinforcing webs 20.

The bushing I0 is preferably sectional to facilitate its insertion inthe rotary table T. In the preferred construction the bushing |0comprises two sections A and B of substantially equal extent asillustrated in Fig. 1 of the drawings. A central vertical opening 2| isprovided in the bushing ID to receive and pass the pipe P, tubing andother drilling equipment. It is afeature of the invention that theopening 2| is of uniform diameter or dimensions throughout its length,that is, the opening 2| has vertical walls and is not tapered or ofdownwardly diminishing capacity. This formation of the opening 2|permits the ready passage of drill pipe protectors and other devicesthroughthe bushing l8 which often interfere with the lower ends of theusual master bushings having central openings of downwardly diminishingdiameter. 'In the particular form of the invention being described theopening 2| is round in cross section or is cylindrical, it beingunderstood that the opening 2| of the bushing l0 may be polygonal, asillustrated in Figs. 6, 8, 9 and 10 of the drawings.

It is a feature of the invention thatlongitudinal or vertical slotsareprovided inthe wall of the opening. 2| to receive the slips l2. Theslots I are circumferentially-spaced to provide for the spacedengagement of the slips |2 with the pipe P. In the drawings I have shownfour equally spaced slots ||,it being understood that the bushing ||lmay be provided with two slots, three slots or any desired number ofslots II, as desired. In accordance with the invention the slipreceiving slots H are of uniform configuration and width throughouttheir lengths and are of substantial length to present'extensive wallsor surfaces for engagement by the slips l2. The opposite side walls ofthe slots I are parallel andare preferably vertical to provide for theeasy insertion of the slips |2. In the particular form 'of the inventionillustrated'in Figs..1 to 5,

inclusive, of the'drawings the inner walls.22 of the slots l arecylindrically concaved. These inner walls 22 of the slots II areinclined downwardly and inwardly to slidably receive the slips 2 and toprovide for the wedging of the slips against the object or pipe P. Thecurvature of the inner walls 22 of the slots is the same throughouttheir lengths having a uniform radius of curvature. The above describedshape and proportions of the slots provide for the full or extensivecontact of the slips l2 with the slot walls. The slots may extend fromthe face or upper end of the bushing H] to the lower end of the bushing.

The slips l2 are provided to grip and suspend pipe P, tubing or otherwell drilling equipment extending through the bushing opening 2|. Theslips |2 are shaped and proportioned to properly fit and operate in theabove-described slots The pipe gripping slips |2 are elongate membershaving fiat parallel opposite sides 23 for cooperating with the sidewalls of the slots H and having cylindrically convexed rear surfaces 24for shiftably bearing on the inner walls 22 of the slots. The curved orconveXed surfaces 25 of the slips l2 are inclined downwardly andinwardly but have the same radius of curvature throughout their lengthstouniformly engage the walls 22. It is to be understood that when theslots H are polygonal or provided with flat inner walls the rearsurfaces 24 of the slips |2 may be flat to have proper cooperationtherewith. When seated in the slots the slips l2 project into thebushing opening 2| to have suspending and gripping engagement with theobject or pipe P.

The active faces or sides of the slips |2 may be suitably roughened ortoothed to properly grip the object or pipe P. The invention, however,provides. simple and particularly effective replaceable plates or liners25 for the active sides of the slips I2. The liners 25 are secured tothe inner or active faces of the slips l2 and are adapted to have directengagement with the object or pipe P and thus assume the wear. The facesof the slips 2 are provided with longitudinal or vertical grooves 26 forreceiving tongues or keys 2'! on the liners 25. The lowerywalls 28 ofthe grooves 26 are inclined downwardly and outwardly. The lower ends 29of the keys 2! are correspondingly inclined to have locking cooperationwith the walls 28. The invention includes simple positive means forremovably securing the liners 25 to the slips l2. Pins or rods 30 areinserted in transverse openings in the slips I2 and the keys 2'! of theliners 25. The ends of the rods 30 may be riveted over whereby the rodsare dependably held against displacement to form positive connectionsbetween the slips and the liners 25. The active faces of the liners 25are cylindrically concaved to conform to the object or pipe P and areprovided with wickers or teeth 3|. The teeth 3| are adapted to havegripping and supporting contact with the pipe P and preferably faceupwardly and inwardly. If desired the teeth 3| may be grooved verticallyto more effectively resist relative rotation between the pipe P and theslip liners 25. The liners 25 may be replaced with liners of differentthicknesses to adapt the slips It! to handle pipe of differentdiameters.

The bodies of the slips I2 are preferably hollow or provided withchambers 32 to be light in weight. Reinforcing webs 33 may extendthrough the chambered interiors of the slips. Guide fingers 34 maycooperate with the surfaces 35 to guide the slips. The slips l2 usuallyproject above the upper surface of the bushing II) when engaging thepipe or object P. The invention provides means for preventing the slipsl2 from falling through or from the slots H. Stop lugs 36 project fromthe upper portions of the slip sides 23 and are adapted to fit inrecesses 36 in the upper face of the bushing ID to limit the downwardand inward movement of the slips l2. The recesses 36 are suitably shapedand proportioned to provide for the necessary play or movement of theslips I2.

The invention provides handles H on the slips I2 to facilitate theirinsertion in and removal from the slots The handles H have forks oryokes 31 on their lower ends extending into recesses 31 in the upperends of the slips |2. Pivot pins 38 pivotally connect the forks 31 withthe bodies of the slips |2. Cams or stop projections 9 may be providedon the forks 31 to limit the inward swinging of the handles H. Thehandles I-I include stems 39 extending upwardly from the forks 31 andlateral heads 39 carried on the stems 39. If desired or found necessarythe ham-- dles H of adjacent slips l2 may be connected whereby two ofthe slips may be handled simultaneously. The rear walls of the recesses31 may be engageable by the handles H to limit the outward and downwardpivoting of the handles.

The rests or cradles l3 are provided to support or carry the slips l2when the slips are withdrawn from the slots and are operable to supportthe slips in positions where they are entirely clear of the bushingopening 2|. A cradle I3 is provided on the bushing ID for each slip l2.The cradles l3 are adapted to be removably secured to the upper end ofthe bushing ID in radial alignment with the slots Each cradle l3includes a leg 40 having a substantially horizontal foot 4|. Recesses 42are provided in the upper side of the bushing Hi to receive the feet 4|.Countersunk or flush plates 43 extend transversely across the upper endsof the recesses 42 and the feet 4| are adapted to be inserted under theplates 43. Clamp screws 44 are threaded through the plates 43 and areadapted to clamp against the feet 4| to securely hold the cradles l3 inplace. The legs 40 project vertically from the feet 4| and have upwardlyand outwardly inclined portions terminating in forks 45. Concavesupports or saddles 46 are arranged on the inclined portions of the legs40 to receive the slips l2. The saddles 46 are shaped and proportionedto properly receive the convex outer sides of the slips.

Means are provided for releasably supporting or holding the slips l2 inthe cradles I3. The forks on the upper ends of the legs 40 have flaringor V-shaped notches 41 adapted to receive handles H. When the slips l2are raised into the cradles l3 the handles I-I may be swung downwardlyso that their stems 39 are engaged in the notches 41. The heads 39 ofthe handles H are adapted to engage against the forks 45 to hold theslips |2 in the cradles l3 in positions where they are entirely free ofthe bushing opening 2|. This elevated or inoperative position of theslips I2 is illustrated in broken lines in Fig. 3. The handles H may beeasily disengaged from the forks 45 to allow the slips I2 to enter ormove downwardly into their respective slots H.

In the use or operation of the assembly illustrated in Figs. 1 to 6,inclusive, of the drawings, the bushing I0 is normally arranged in thetable T as illustrated in Fig. 1 of the drawings. When it is desired toengage or suspend a pipe P passing through the bushing opening 2| theslips l2 are introduced into the slots H and allowed to fit downwardlytherein until their liners 25 grip the pipe P. The operator or operatorsmay readily disengage the handles H from the forks 45 to allow the slipsl2 to slide downwardly in the saddles 46. The fingers 34 on the lowerends of the slips readily guide the slips into the slots The slips arefree to move downwardly in the slots until the toothed inner sides ofthe liners 25 grip or contact the pipe P. The convex outer rear sides 24of the slips |2 have full, even bearing engagement with the walls 22 ofthe slots regardless of the vertical positions assumed by the slips l2when they contact the pipe P. The engagement of the surfaces 24 with theslot walls 22 also maintains the active inner sides of the liners .25vertical to properly grip the pipe P. The fit of the slips l2 in theslots H is such that the pipe is dependably gripped and supported. Dueto the fact that each of the slips l2 has uniform and completeengagement with the inner wall 22 of its respective slot H the severalslips have even or equal engagement with the pipe P to dependably gripthe pipe without distorting it. The slips |2 engaging in the slots IIare adapted to form a positive drive for the pipe P in the event it isdesired to rotate the pipe. The fiat parallel sides 23 of the slips Hare adapted to engage the side walls of the slots II for thetransmission of turning forces.

When the slips l2 are no longer required they may be easily pulledupwardly and outwardly to rest in the saddles 46. swung downwardly toengage the stems 39 in the notches 41 so that the slips are held in thecradles H3. The slips |2 are very easy and convenient to manipulate andare light in weight. The cradles |3 may be easily disengaged from thebushing Ii]. The various parts of the assembly are simple andinexpensive of manufacture. The slots may be cored in the bushing I0 andthe slips l2 do not require special machining. The liners 25 of theslips l2 may be sections of strips or long stock of the desired crosssection and are very inexpensive to manufacture.

The form of the invention illustrated in Figs. 6 to 9, inclusive, of thedrawings includes, generally, a master bushing 5|! having internal slots5|, slips 52 for arrangement in the slots 5| to grip a pipe P or thelike and means 53 for preventing displacement of the slips and forsupporting the slips 52 when they are moved to positions at the upperends of the slots 5|.

The bushing 53 is intended for arrangement in the opening of a rotarytable. The bushing 53 may be shaped for arrangement in the table Tillustrated in Fig. 1 of the drawings or may be polygonal or square,asillustrated in Figs. 6 and 9 of the drawings for arrangement in atypical rotary table. It is to be understood that the bushing is adaptedto be supported in a rotary table to be driven or rotated thereby. Acentral vertical opening 54 is provided in the bushing 50 to pass thepipe P and other drilling equipment. In accordance with the form of theinvention being described the opening 54 is polygonal or square in crosssection. The opening 54 may be round or cylindrical if desired. Theopening 54 is of uniform width or dimensions. throughout its length,having vertical Walls. This is important as it permits the easy freepassage of the drilling equipment through the bushing 50.

The handles H may be The bushing 53 is preferably sectional for readyassembling in a rotary table. As shown in the drawings the bushing 50preferably includes two sections M and N. The bushing 55 is preferablydivided or separated in a vertical plane which intersects two side wallsof the opening 54. In the preferred construction the slots for receivingthe slips 52 occur in the corners of the openings 54. The slots 5| arepreferably alike in size and shape and there may be one slot 5| in eachcorner of the opening 54. It is to be understood that the inventioncontemplates the provision of two or more slots 5| in the bushingopening 54. In the form of the invention being described the slots 5|are polygonal or flat walled. The side walls of the slots 5| are flatand vertical and lie in planes tangent to a circle concentric with thecentral longitudinal axis of the opening 54. The parallel relationshipand, therefore, the uniform spacing of the side walls of the slots 5|continues throughout the entire lengths of the slots. The slots 5| mayextend between the upper and lower ends of the bushing 55. The innermostwalls or inner walls 55 of the slots 5| are fiat and are inclineddownwardly and inwardly. Curved or inclined surfaces 56 join the upperends of the slots 5| to assist in entering or guiding the slips 52 intothe slots.

The slips 52 are adapted to be inserted in the slots 5| to grip andsuspend the pipe P or other object. The several slips 52 are alike andthere is preferably a slip 52 provided for each slot 5|. The slips 52are shaped to properly fit the slots 5| having flat parallel sides 51and downwardly and inwardly inclined rear surfaces 58 for shiftablybearing on the inclined walls 55 of the slots. The slips 52 arepreferably proportioned to have proper play or clearance in the slots5|. The active sides of the slips 52 are preferably vertical and ifdesired teeth or gripping parts may be formed directly on the slips tocooperate with the pipe P. It is preferred, however, to providereplaceable shoes or liners 59 on the slips 52 for gripping the pipe P.The slips 52 are shaped to receive the liners 59 having verticalchannels or grooves 6|] which terminate at their lower ends indownwardly and outwardly inclined walls 6|. Tongues or keys 62 areprovided on the liners 59 to fit the grooves 60 to form positive drivingconnections between the liners and slips. The lower ends of the keys 62are inclined downwardly and outwardly to have locking cooperation withthe groove walls 6|.

Means is provided for removably attaching the liners 59 to the slips 52.Rivets or rods 63 are passing through transverse openings in the slipsand keys 62 to secure the liners 59 to the slips. The opposite ends ofthe rods 63 may be headed or riveted. The active faces of the liners 59are cylindrically concaved to conform, generally, to the pipe P and areprovided with suitable wickers or teeth 64. The teeth 64 preferably faceupwardly and inwardly and may be interrupted by vertical grooves to havemore efficient engagement with the pipe. The liners 59 may be replacedby liners of various thicknesses to adapt the slips 52 for the properhandling of pipe and other objects of various diameters. The bodies ofthe slips 52 may be chambered or hollowed to be light in weight.Reinforcing webs 65 may extend through the hollow interiors of theslips. Handles H are provided on the slips 52 to facilitate themanipulation of the slips. The handles H may be identical with thehandles H described above and reference is hereby made to the detaileddescription of the handles H. Corresponding reference numerals areemployed to designate corresponding parts of the handles H and H andtheir mountings.

The means 53 is provided to prevent loss or displacement of the slips-52 from the slots 5| and to assist in supporting the slips in retractedor inoperative positions at the upper ends of the slots. The means 53comprises elongate grooves or slots in the side walls of the slipreceiving slots 5|. There may be a slot 10 in each side wall of eachslot 5|. The slots 1|] are parallel with the inclined inner walls 55 ofthe slots 5| and terminate some distance above the lower ends of theslots 5|. Lugs or pins 7| project from the sides of the slips 52 toshiftably operate in the slots 10. The cooperation of the pins II withthe slots 10 is such that the slips 52 may properly work and shift inthe bushing slots 5| The pins 1| are adapted to cooperate with the lowerends of the slots 10 to definitely limit the downward travel of theslips 52 and thus prevent the loss of the slips from the bushing 5|].The upper ends of the slots are spaced some distance below the upper endof the bushing 59. The slots 10 and the pins 7| are related so that thepins cooperate with the upper ends of the slots 10 when the slips 52 arebrought to positions where they may be pivoted onto the surface 56. Thecooperation of the pins 1| with the upper ends of the slots 70 assistsin retaining or supporting the slips 52 in their up or inoperativepositions on the surfaces 55. Fig. 7 of the drawings illustrates inbroken lines a slip 52 in its retracted position where it rests on thesurface 55 with the pins H in cooperation with the upper ends of theslots 15. In practice removable plates 73 may be recessed or countersunkin the upper ends of the bushing 55 to close the upper ends of the slots10. The plates 13 thus form the upper ends or walls of the slots 15 andmay be removably secured to the bushing by screws or other suitablemeans. The plates. 13 are removable to permit the entrance of the pins1| in the slots 10 when the slips 52 are assembled in the bushing 50 andare removable to permit the withdrawal of the pins 1| from the slots 15when the slips are to be removed from the bushing.

It is to be understood that the invention contemplates the embodiment ofcradles similar to the cradles 53 described above, in the form of theinvention illustrated in Figs. 6 to 9, inclusive, of the drawings, insubstitution for the means 53 just described, and contemplates theembodiment of the means 53 in the form of the invention illustrated inFigs. 1 to 5, inclusive, of the drawings in substitution for the cradlesI3.

The use or operation of the assembly illustrated in Figs. 6 to 9,inclusive, of the drawings is substantially the same as the operation ofthe previously described form of the invention. The slips 52 maybeeasily passed downwardly into the slots 5| to contact and grip the pipeP. The handles H facilitate the lowering of the slips and the pins 1|cooperating with the slots 10 effectively enter the lower ends of theslips in the slots. As the slips 52 move downwardly in the slots 5|their rear surfaces 58 contact the inner regardless of the verticalpositions assumed by the slips when they contact or grip the pipe.Accordingly, the slips 52 assume equal loadsin suspending or engagingthe pipe. The flat sided slips 52 fitting in the flat sided slots 5|cannot possibly tilt or turn and are adapted to form positive effectivedrives in the event it is desired to rotate the pipe. The liners 59 areoperable to obtain firm dependable gripping engagement with the pipe Pwithout subjecting the bodies of the slips proper to wear. When theslips 52 are no longer required to grip the pipe P they may be easilyand quickly removed from the slots 5|. The slips 52 may be easily pulledupwardly from the slots to positions where they are supported on thesurfaces 56 with their pins 1| bearing on the plates 13 which form theupper walls of the slots 10. The cooperation of the pins H with theupper ends of the slots operates to retain the slips in their inactivepositions on the surfaces 56. The bushings 50 and the slips 52 aresimple and easy to manufacture. The slots 5| may be cored directly inthe sections of the bushing 5|! and the slips 52 do not requireextensive machining. The liners 59 may be easily replaced to reconditionthe slips 52 or to adapt the slips for the engagement of pipes ofdiiierent diameters.

Fig. 10 of the drawings illustrates a form of the invention embodying amaster bushing 80 comprising two unequal sections X and Y. The bushings80 may be of the same configuration as the bushing H] or the bushing 50.In the particular case illustrated the bushing 80 is of the same generalconfiguration as the bushing 50. The polygonal opening 8| of the bushing85 has flat walled slots 82 in its corners for receiving slips 83. Theslips 83 may be identical with the slips 52. The bushing 8|) is dividedinto the two sections X and Y in a vertical plane 85 spaced from thecentral longitudinal axis of its opening 8|. The line or plane 85 ofdivision of the bushing 80 preferably angularly intersects two adjacentsides of the polygonal opening 8|. When the bushing 85 is divided inthis manner one section X has three slots 82 while the other section Yhas one slot 82. Where the one section X carries three slips 83 thebushing 8|] cannot spread or work and a very positive suspension orgripping engagement with the pipe P is obtained. The operation and themode of handling the slips 83 are the same as described above inconnection with the slips 52.

When I use the term liner I refer to the shoe or shoe-like part thatactually engages the pipe or the object handled.

Having described only typical preferred forms and applications of myinvention, I do not wish to be limited or restricted to the specificdetails herein set forth, but wish to reserve to myself any variationsor modifications that may appear to those skilled in the art or fallwithin the scope of the following claims:

Having described my invention, I claim:

1. A bushing for a rotary table comprising a body having a polygonalopening of unvarying width, and having slots in the walls of the openingfor receiving slips.

2. In combination, a bushing for a rotary table having a polygonalopening for receiving a piece of drilling equipment, and havinglongitudinal slots in the corners of the opening, said slots havinginclined walls, and slips arranged in the slots to grip the piece ofequipment and having inclined surfaces cooperating with said walls.

3. In combination, a bushing for a rotary table having a polygonalopening forreceiving a piece of drilling equipment, and havinglongitudinal slots in the corners of the opening, said slots havingsubstantially parallel side walls and downwardly and inwardly inclinedinner walls, and slips shiftably fitting the slots to grip the piece ofequipment.

4. In combination, a bushing for a rotary table having an opening forreceiving a piece of drilling equipment, and having spaced slots in thewall of the opening provided with parallel side walls and cylindricallyconcaved inner walls, and slips in the slots for engaging the piece ofequipment and having parallel sides and cylindrically convex rear sidesfor cooperating with the walls of the slots.

5. A slip for arrangement in a rotary table bushing comprising a slipbody having substantially parallel sides, and a downwardly and inwardlyinclined rear surface, and means projecting from the lower end of theslip body for guiding it in a slot in the bushing.

6. A slip for arrangement in a rotary table bushing comprising a slipbody having substantially parallel sides, and a cylindrically curveddownwardly and inwardly inclined rear surface extending between saidsides, and means on the active face of the slip body for engaging anobject extending through the bushing.

7. A master bushing comprising a body having a polygonal opening withsubstantially vertical walls, and having substantially vertical slots inthe corners of the opening, said slots having substantially parallelside walls and inclined inner Walls.

8. A master bushing comprising a body having an opening with acylindrically curved wall, and having spaced vertical slots in the wallof the opening, said slots having substantially parallel side walls andinclined inner walls.

9. Apparatus of the character described comprising a master bushinghaving a polygonal opening with substantially vertical walls and havingsubstantially vertical slots in the corners of the opening, said slotshaving substantially parallel side walls and inclined inner walls, andslips arranged in the slots to grip an object extending through theopening, the slips having substantially parallel sides and inclinedsurfaces for cooperating with the inclined walls of the slots.

10. Apparatus of the character described including a master bushing fora rotary table, the bushing having an opening for passing drillingequipment and slots in the wall of the opening, gripping slips adaptedfor insertion in the slots, and stationary cradles carrying the slipsfor ready entrance to the slots.

11. Apparatus of the character described including a master bushing fora rotary table, the bushing having an opening for passing drillingequipment and slots in the wall of the opening, gripping slips adaptedfor insertion in the slots, stationary cradles on the upper side of thebushing for supporting the slips in radial alignment with the slot forinsertion therein.

12. Apparatus of the character described including a master bushing fora rotary table, the bushing having an opening for passing drillingequipment and slots in the wall of the opening, gripping slips adaptedfor insertion in the slots, handles on the slips, cradles for supportingthe slips above the openings, and parts on the cradles cooperable withthe handles to releasably retain the slips on the cradles.

13. In combination with a rotary table bushing and a slip for usetherein, a cradle for supporting the slip comprising a support to bemounted on the bushing, and a saddle on the support for carrying theslip.

14. In combination with a rotary table bushing and a slip for usetherein, a cradle for, supporting the slip comprising a support to bemounted on the bushing, and a saddle on the support having a concavesurface inclined downwardly and inwardly toward the opening of thebushing to receive the slip.

15. In combination with a rotary table bushing, a slip for use in thebushing, a handle on the slip, a support on the bushing, a saddle on thesupport for carrying the slip, and a fork on the support engageable bythe handle to retain the slip in the saddle.

16. A rotary table bushing comprising a body having a vertical openingand circumferentially spaced slots in the wall of the bushing, the bodybeing divided in a vertical plane spaced from the central axis of theopening to comprise two sections, one of said sections having more slotsthan the other.

17. In combination, a rotary table bushing having an opening for passingdrilling equipment, there being a slot in the wall of the opening havingan inclined inner Wall, and a groove in a side wall of the slotsubstantially parallel with said inclined wall, a seat at the upper endof the slot, a slip shiftable in the slot operable to engage an objectin the opening and shiftable to a retracted position on the seat,-and aprojection on the slip operable in the groove and cooperable with theupper end of the groove to retain the slip on the seat.

18. In combination, a rotary table bushing having an opening for passingdrilling equipment, there being a slot in the wall of the opening havingan inclined inner wall, and a groove in a side wall of the slotsubstantially parallel with said inclined wall, a slip shiftable in theslot operable to engage an object extending through the opening, and aprojection on the slip operating in said groove to prevent displacementof the slip from the slot.

DENNIS L. DRISCOLL.

